Field of the Invention
The present invention relates to a technique of generating a panoramic image using captured images of an image capturing device whose imaging direction can be changed.
Description of the Related Art
A panoramic image is used in a network camera. The panoramic image is an image for allowing a range wider than the angle of view of a camera to be observed by joining a plurality of images captured in a plurality of imaging directions within the movable range of the network camera. The user can grasp the current camera direction and change the camera direction to a desired one by using the panoramic image.
A panoramic image is created by joining a plurality of images obtained by fixing the zoom value of the camera, and repeating an operation of moving the imaging direction by the pan and tilt and an image capturing operation so as to cover the movable range of the camera. Japanese Patent Laid-Open No. 11-008845 discloses a method of creating a panoramic image by mapping, to a virtual spherical surface, a plurality of images captured within the movable range of a camera and joining the images. In addition, Japanese Patent Laid-Open No. 2008-099184 discloses a technique of creating a panoramic image based on designation of a panoramic image generation range by the user.
When creating a panoramic image, an image capturing operation is generally performed at the zoom wide-angle end to decrease the number of images to be captured. On the other hand, a network camera emphasizing a telescopic function has an angle of view narrower than that of a normal camera even at the wide-angle end. If the angle of view of the camera is narrow, the number of images to be captured by a camera to create a panoramic image of the same range is larger than that when the angle of view is wide, thereby prolonging a period necessary to perform an image capturing operation.
When, for example, a monitoring target by a network camera is limited to some imaging directions within a movable range, a panoramic image for allowing the whole movable range to be observed is not necessary. In other words, if a panoramic image is created by capturing the whole movable range, an image of a range which is not generally observed may be captured.